March 7, 2026

Summary

Enterprise organisations, particularly those operating in regulated sectors like finance and insurance, often manage complex and heterogeneous IT estates. This diversity stems from organic growth, mergers, and acquisitions, resulting in a wide array of endpoints and system configurations. For a managed security service provider, delivering consistent and effective security controls across these varied client environments presents a significant operational challenge. A standardised approach is required to ensure a high-quality, repeatable security posture without the overhead of bespoke engineering for every client engagement.

Challenge

The primary challenge was to systematically harden client endpoints and reduce their attack surface at scale. A one-size-fits-all policy is impractical as it risks disrupting unique line-of-business applications. The core task was to develop a security framework that was both robustly standardised against industry benchmarks and sufficiently flexible to adapt to the specific technical and operational needs of individual clients. The solution needed to be transferable and efficient, enabling consultants to deploy and manage advanced security controls without lengthy, manual configuration for each new environment.

Objectives

The programme was guided by a set of clear objectives:

• To design and create a standardised set of Attack Surface Reduction (ASR) policies aligned with Center for Internet Security (CIS) hardening benchmarks.
• To develop a ‘plug-and-play’ deployment methodology that could be efficiently transferred and adapted across different client environments.
• To leverage configuration-as-code principles to ensure deployments were repeatable, consistent, and easily auditable.
• To improve the efficiency and quality of security service delivery by refining the onboarding process for Microsoft Defender for Endpoint.
• To verifiably improve client security posture by systematically reducing the vectors available for potential cyber-attacks.

Approach and Delivery

A methodical approach was taken, beginning with comprehensive security posture assessments for each client. Using automated tooling and PowerShell, client networks and architectures were mapped to determine how security controls could be integrated without causing business disruption. This discovery phase was crucial for tailoring the subsequent hardening measures.

Based on these findings, a foundational framework of CIS-compliant ASR rules was developed for Microsoft Defender for Endpoint. This framework was engineered as a series of adaptable policies within Microsoft Intune. The key to its portability was the extensive use of PowerShell to script the configurations, embodying a configuration-as-code (CaC) model. This allowed for rapid, repeatable, and consistent deployments across multiple enterprise clients, forming a core component of the Managed Detection and Response (MDR) onboarding process.

Technical Implementation

The solution was built on the Microsoft security ecosystem. Microsoft Defender for Endpoint and Defender for Cloud provided the core endpoint protection and cloud security posture management capabilities. Microsoft Intune was used as the central management plane to deploy and enforce the ASR policies on endpoints.

The ‘plug-and-play’ policies were created as a series of PowerShell scripts and Intune configuration profiles. These applied CIS hardening techniques directly to Defender settings, creating a robust baseline. This code-based approach ensured that the framework was easily transferable and version-controlled. For each client, the baseline could be deployed efficiently, with documented procedures for tuning specific rules to accommodate unique application requirements, thereby balancing security with operational stability.

Outcome

The programme successfully produced a scalable and portable framework for implementing Attack Surface Reduction across a diverse portfolio of enterprise clients. This resulted in a consistent, high-quality security uplift, particularly for organisations in heavily regulated industries.

The configuration-as-code approach significantly improved the efficiency and reliability of service delivery, reducing the manual effort required for endpoint hardening. Clients benefited from a systematically reduced attack surface, lowering their overall risk profile. The framework became a valuable internal asset, streamlining the onboarding process for new MDR customers and contributing to the successful delivery of advanced security specialisations.

Risks, Controls and Governance

A key risk was the potential for stringent ASR rules to impact the functionality of legacy or bespoke client applications. This was mitigated through several controls. The initial in-depth security posture assessment identified critical systems and potential conflicts. Furthermore, policies were designed to be adaptable, not monolithic, allowing specific rules to be set to audit mode or disabled on a per-client basis following a documented change control process.

Strong governance was maintained throughout. All deliverables were documented in detailed Statements of Work (SOWs) and supported by high-quality change request documentation. This ensured full transparency and provided clients with a clear audit trail for all security enhancements implemented in their environment.

Key Lessons

The project reinforced several key principles for delivering security services at scale. Firstly, adopting a configuration-as-code model using tools like PowerShell is fundamental to achieving scalable, repeatable, and consistent outcomes in a multi-client environment. Secondly, building frameworks upon established industry benchmarks like CIS provides a credible and effective foundation for security hardening. Finally, designing security policies to be modular and adaptable�’plug-and-play’�is crucial for balancing standardisation with the unique operational needs of each enterprise, ensuring that security enhancements can be delivered without compromising business continuity.

Related Services

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• CIS Intune Benchmark Assessment
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• Microsoft Intune Deployment & Optimisation
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